O let not the oppressed return ashamed - Ashamed by being disappointed, as if they had trusted in that which had no claims to confidence. Compare the notes at Job 6:20. The word rendered “oppressed,” means “trodden down, crushed, broken, afflicted.” It refers to the people as attacked by foreign armies, or as crushed by those who had gained power over them. The word “return” refers to their coining back from God - from the throne of mercy. Let them not come back from thee with no assurance of thy favor; with no evidence that their prayers have been heard; let them not come back, subject to the reproach that they had made their appeal to thee in vain.
Let the poor and needy praise thy name - The people who are oppressed and helpless. Let them have occasion to praise thee because their prayer has been heard, and because thou dost save them.